James



March 17, 1964 J. E. DORE & 3

REFRACTORY STOPPER FOR ALUMINUM CASTING APPARATUS AND METHOD OF CASTING Filed April e, 1962 ATTORNEY United States Patent Q 24,854 REFRACTORY STOPPER FOR ALUMINUM CAST- ING APPARATUS AND METHOD OF CASTING James E. Dore, Milford, Coran., assignor to Ka ser Aluminum & Chemical Corporation, Oakland, Calif., a corporatior of Delaware Filed Apr. 16, 1962, Ser. No. 187,827 11 Claims. (Ci. 22-84) This nvention relates to the handling and control of molten metal. More particularly this invention relates to a method and apparatus for releasing and stopping the flow of molten metal from a source thereof, eg., a furnace or other molten metal receptacle. This application is a continuation-in-part of my copending application Serial Number 649,448, filed March 29, 1957.

In the casting of metal, e.g., aluminum and aluminum alloys, it is common practice to provide a body of molten metal in a suitable holding receptacle, eg., an open hearth or reverberatory furnace, electrical resistance heated furnace or induction heated furnace. The open hearth furance, which may be oil, gas, coal or coke fired, is conmonly used for supplying molten metal for casting and may comprise a melting hearth and a holding hearth. In preparing the metal for casting the charge of metal and any desired alloying constituents to be melted are generally added in the melting hearth and thereafter the molten metal is transferred to the holding hearth, generally by means of run-around troughs, where it is subjected to cleaning treatment and where control may be had of the composition and temperature of the molten bath. The treated molten metal may then be transferred from the holding hearth to the casting station by suitable means, such as a trough. Also, in certain instances the molten metal may be tapped from the holding hearth into a heated holding ladle and the ladle moved to the casting station where the molten metal is poured into suitable transfer troughs. In handling the molten metal as above described, it is necessary to provide means tor releasing and stopping flow of molten metal from the melting hearth to the holding hearth and from the holding hearth to the casting station or ladle.

According to prior art practice releasing and stopping the flow of molten metal is accomplished by nserting a conical plug of a suitable molten metal resistant material, known in the art as a check-rod tip, in the molten metal outlet. The use of such a conical plug by itself is completely unsatisfactory since even a slight amount of wear of the contact surfaces of either the plug or the outlet results in uneven contact between the plug and the outlet whereby molten metal may escape. Accordingly, it is customary in the prior art to coat the conical plug With material such as a mXture comprising fiour and water. This material is known in the art as dough and the operation of sealing the tap hole by such means is referred to as doughballing This dough performs two functions. First, it fills any discontinuities in the outlet, thus providing a tight seal and second, the carbonization of the flour provides a weak bond which prevents the metal head in the furance from forcing the plug out of the orifice.

Such practice possesses many inherent disadvantages, particularly with regard to casting aluminum where it is desired to produce high quality metal with a minimum of porosity and inclusions and where it is desired to transfer the molten metal at a very rapid rate. The bond formed by the carbonization of the flour is quite weak. This makes it difficult to obtain a leakproof seal when doughballing against relatively high metal heads. The trend in present day practice is to employ higher and higher heads of molten metal in receptacles. When employing doughballing' the maximum head which may be employed is very limited. With such practice high heads result in leaky seals which may cause hazards to safety, production delays and damage to casting equipment. In addition, the weak bond of the dough limits the size of the outlet which can be successfully used. Even in the plastic stage the "doughball material possesses very little strength. This makes closure of the taphole diflicult at high metal velocities because of the washing action of the metal. Present day practice calls for higher metal flow rates requiring larger openings. Under prior art practices employing "doughballing' it is necessary to use a plurality of outlet openings and often even a plurality of transfer troughs when such high flow rates are employed. Such arrangements are bulky, expensive and require an excessive amount of space.

Further, when a furnace is tapped, a portion of the carbonized "doughball remains in the outlet. If this material is not removed regularly, buildup in the outlet occurs, thereby restricting the metal flow from the outlet. The doughball material contains water and carbonaceous matter which represents a potential source for gassing the metal resulting in porosity in the ultimate cast body. The carbonized doughball material is quite friable and breaks up into pieces when the furnace is tapped. These fragments represent a potential source of non-metallic inclusions.

Accordingly, the primary purpose and object of this invention i& to provide an improved method and apparatus for releasing and stopping flow of molten metal from molten metal holding receptacles which eliminates or substantially reduces many of the disadvantages of the prior art techniques.

Another object of this invention is to provide a novel method and apparatus for releasing and stopping the flow of molten metal from molten metal holding receptacles wherein high molten metal heads and high flow rates may be employed with a single outlet opening.

Another object of this invention is to provide a novel method and apparatus for releasing and stopping flow of molten aluminum metal from a receptacle for molten aluminum wherein such defects as porosity and inclusions may be eliminated or substantially reduced in the ultimate cast body.

Another object of this invention is to provide a novel apparatus for releasing and stopping molten metal flow from a molten metal receptacle whereby the problem of buildup of material in the outlet is eliminated or substantially reduced and adequate metal delivery is assured.

Other objects and advantages of this invention will be apparent from the following description thereof in conjunction with the accornpanying drawing.

In accordance with this invention, releasing and stopping the flow of molten metal from a molten metal holding receptacle is accomplished by the combination of a tapping block provided with an orice for passage of the molten metal, a plug which partially fits within said orifice and which in part is of a shape or configuration wherein substantially a line of contact may be made between the outer peripheral surface of said plug and the inner periphery of said orifice, and a resilient refractory material covering the plug in the area of contact between the plug and the orice. In a preferred embodiment of this invention the plug is substantially conical in shape and by the term conical, as used hereinafter, is mea-nt a cone, a frustrurn of a cone or a cone with a rourded tip. However, it will be understood by one skilled in the art that the plug can be of a shape other than conical, as heretofore defined, the important feature being that the shape or configuration of the Contacting portions of the plug and orifice be such that substantially a line of contact may be made between the outer peripheral surface of the plug and inner periphery of the orifice.

Panted Mar. 17, 1964,

For example, the plug could be spherical or semi-spherical in shape or semi-spherical with a flat top or end portion. Likewise, the orifice can take various shapes, e .g., completely cylindrical, cylindrical only as to the portion adapted to contact the plug, or any other shape in that portion adapted to contact a plug of a compatible shape so as to provide for substantially a line of contact, as aforesaid.

When the plug is inserted .in the orifice, the resilient refractory material -follows the contour of the orifice and plug as it is compressed. This fil-ls any discontinuities in the orifice and plug, thus providing a seal to stop the flow of molten metal. Suitable mechanical means is then provided to hold the plug in place.

For purposes of more satisfactory illustration, this invention will be specifically described with 'reference to the embodiment shown in the accompanying drawing which comprises an elevational view in cross section of a nolten metal receptacle illustrat-ing the novel tapping block, plug and resilient refractory coverng material of this invention.

Referring now more particularly to the drawing, there is shown a -tapping block provided with a taphole or orifice 23, a plug 1 -fabricated -from a suitable material, such as cast iron, steel or molten aluminum resistant refractory and a resilient refractory material cover 2 for the plug. In this embodment, the plug is substantially conical in shape and the orifice is cylindr ical. The molten metal body 3 is contained in a suitable holding receptacle 4. The plug is suitably mounted on a control rod 6 by means, such as external threads 24 on control rod 6 and internal threads 25 in the plug. A lock nut 26 may be provided to prevent loosening of the threaded connection between conical plug 1 and rod 6.

It has been found that to obtain complete closure of orifice 23 and stoppage of molten meta-l flow, it is desirable to freeze a small amount of metal 22 generally taking the form of a thin film between cover 2 and orifice 23 to form a complete seal.

The design of the orifice and plug must be such that upon insertion of -the plug in the orifice, substantially a line of contact will be made between the outer periphery of the plug and the inner periphery of the orifice. The included `angle between the outer surface of the plug and the inner surface of the orifice is less than 45. in order to avoid cutting of cover 2 by the Contacting edge of the orifice, this edge is slightly beveled. Accordingly, a sharp line of contact would not be made. However, since only a slight bevel is employed, substantially a line of contact is made. For Simplicity in the description, the contact will hereinafter be referred to as a line of contact. In such an instance 'where the plug is covered with a resilient refractory cover 2, the cover is compressed at the line of contact and thus the surface of the cover in the zone immediately adjacent the line of contact is more or less parallel to the inner surface of the orifice. Thus, 'the metal 22 filling the annular space between the plug and the inner surface of the orifice in the Zone adjacent the line of contact generally takes the form of a thin film which is close to the outside of the orifice and thus at a lower temperature than the main body of molten metal 3. Such lower temperature is generally sufficient to freeze this thin film of metal 22 thereby providing a ti ght seal. In some instances where the plug is tabricated from a material having a high heat conductivity, such as cast iron, the heat from the molten metal may be conducted through the plug to the metal 22 and prevent it from freezing. Accordingly, in such instances, it is necessary that the resilient refractory material cover completely cover the portion of the plug within the orifice for insulation purposes as shown in the drawing. Where, due to selection of material, the heat conductivity of the plug is not high enough to prevent the above-mentioned freezing cover 2 only needs to cover the area of contact between the plug and the orifice.

Generally, it has been found that where a small amount of metal 22 is not rozen near the line of contact between the plug and the orifice the stoppage of molten metal may not be permanent and it may eventually seep out around the plug. In order for the metal 22 to take the form of a thin film which may be easily frozen it is essential that the included an-gle between the surface of the plug and the inner surface of -the orifice be less than 45.

In addition, it is desirable to provide a free space 28 around the portion of plug 1 on the downstream side of orifice 23 to prevent freezing of molten metal around the portion of the plug which -is not inserted within the orifice. Freezing of metal around such a large surface area of the plug would make it difiicult or impossible to remove the plug.

The type of refractory material for cover 2 is of primary importance. It must be compressible and resilient at high temperatures, particularly in the range of 1200 F. to 1800 F. In addition, it must possess Chemical resistance to attack by the molten metal. lt has been found that aluminum-silicate fiber materials are best suited for use with molten aluminum. By the term "aluminum-silicate fiber material is meant materials obtained by melting and fiberizing miXtures of alumina and silica with or without modifying agents, such as borax glass, zirconia and soda ash. Available commercial materials of this type, suitable for this application are known under the :trade names of Fiberfrax" and Thermofiex. One example of such type of material suitable for this application comprises 512% Al O 475% SiO 0.6% Bgoa, 0.6% Na O, balance iMgO, CaO, Fe o and mpurities in minor amounts, Cover 2 may be -fabricated in several ways. First, it may be -fabricated from successive layers of aluminum-silicate fiber paper wrapped around the plug until a cover of the desired thickness is obtained. Second, the cover may be fabricated initially in the desired shape using conventional manufaeturing techniques.

In order to maintain stoppage of molten metal flow, suitable means 'for positively positioning plug 1 in tapping block 5 is required. One such means is shown in the drawing and comprises a pair of hook members 9 pivotally mounted on a suitable shaft 10, which in turn is mounted by means of a pair of members 27 on a metal plate 11, afiixed to the shell 12 of holding receptacle 4, Suitable spring members 13 may be provided between the hook members and a suitable plate 14 afiixed to metal plate 11 by suitable means such as Welding. Thus, spring members 13 tend to urge the hook members toward the inside of receptacle 4. The travel of the hook members is limited by suitable stop members 16.

While the hook members, members 27, spring members 13 and stop members 16 are employed in pairs, only one member of each pair is shown in the drawing. The second member of each pair is spaced from, operates in the same manner as and -is identical to the first. Accordingly, illustration of one member of each pair in the drawing will sufiice for both since -the operation and function of both members of each pair ris apparent from the drawing and description.

Control rod 6 may be supported from the hook members by means of a shaft 17 axed to a bar 13 by suitable means, such as welding, which bar in turn is suitably afiixed to control rod 6 by suitable means, such as welding. When the end portions of shaft 17 are positioned in the hook members, the tension on the spring members forces control rod 6 toward tap hole or orifice 23, thus forcing the plug into the orifice. The stop members 16 are positioned such that the hook members will not contact the stop members before the plug Contacts the orifice. To insure that shaft 17 remains within the hook members, a pair of suitable bar members 19 are mounted on shaft 10 by suitable ring members 20. One bar member 19 operates in conjunction with each hook member and illustration of one sufces for both. Ring &124354 members 20 are free to turn relative to shaft 10. Normally, gravity maintains each bar member 19 against its respective hook member in a position whereby shacfit 1*7 is prevented from moving upwardly out of hook members 9. However, to remove the shafit 'from the hook members, bar members 19-may be moved in an arcuate path away 'from the hook members in a counter clockwise direction of the drawing whereby the shaft may be moved upwardly and out of the hook members.

In order to permit the flow of molten metal, it is merel necessary to pull control rod 6 away from tap hole 7 through the use of a suitable handle 21 against the tension of spring members 13. If it is desired to allow the molten metal to continue to flow, bar members 19 are simply moved out of position, shaft 17 is moved upwardly and out of hook members 9 and control rod 6 and plug 1 are completely removed from the tapping block 5. When it is desired to stop molten metal flow, the plug is engaged with the orifice, bar members 19 are moved out of position and shaft 17 is replaced in the hook members, after which the bar members are allowed to return by gravity to their normal position. The hook members will then support control rod 6 and force the control rod towards the orifice through the action of spring members 13 thereby forcing the plug into the orifice thereby stopping metal flow.

An apparatus as shown in the drawing and described above was employed on an aluminum melting and holding furnace and operated successfully. This apparatus employed an orifice 23 having a true cyclindrical bore and a conical plug 1 of a configuration shown in the drawing having a cone angle of 39. This resulted in an angle of about 20 between the outer surface of the plug and the inner surface of the orifice. The plug employed was cast iron and the tapping block 5 was fabricated from a high alumina castable refractory manufactured and sold under the trade name Purotab. The resilient refractory fiber cover 2 employed comprised three conically shaped layers of .O20" thick aluminumsilicate paper of the type known under the trade name Fiberfrax. It has been found that a cover made from this material may be re-used several times before replacement is necessary.

As used herein, the term aluminum is meant to cover high purity aluminum, commercial purity aluminum and aluminum alloys.

While this invention has been shown and described in connection with one specific embodiment thereof, it will be apparent to one skilled in the art that the invention is by no means limited thereto, but that many modifications may be made without departing from the spirit and scope thereof.

What is claimed is:

1. An apparatus for releasing and stopping the flow of molten metal from a molten metal holding receptacle comprising a tapping block provided with an orifice having a true cylindrical bore, a conical cast iron plug which partially fits within said orifice wherein a line of contact may be made between the outer peripheral surface of said plug and the inner periphery of said orifice, a resilient ref'actory fiber material covering said conical plug in the area of contact between said plug and said orifice, said resilient refractory fiber material being characterized by resistance to attack by molten aluminum and the ability to retain its resilience at temperatures ranging from 1200 F. to 1800 F., the included angle between the outer surface of said conical plug and the inner surface of said orifice being about 20 when said plug is in position in said orifice.

2. The apparatus of claim 1 wherein said resilient refractory fiber material is an aluminum-silicate material.

3. The apparatus of claim 2 wherein said resilient refractory fiber material completely covers the portion of said conical plug within said orifice.

4. An apparatus for releasing and stopping the flow of molten metal from a molten metal holding'r'eceptacle comprising a tapping block provided with an orifice having a true cylindrical bore, a conical cast iron plug which partially fits within said orifice wherein a line of contact may be made between the outer peripheral surface of said plug and the inner periphery of said orifice, an aluminumsilicate fiber material covering said conical plug in the area of contact between said plug and said orifice, the included angle between the outer surface of said conical plug and the inner surface of said orifice being about 20 when said plug is in position in said orifice, and spring means for maintaining said plug and covering in tight contact within said orifice.

5. In a method of handling molten aluminum metal wherein a body of molten metal is provided in a holding receptable and molten metal is passed therefrom through an opening in said holding receptacle, the improvement for stopping flow of molten metal through said opening comprising the steps of closing said opening with a resilient refractory fiber surface, said surface extending partially into said opening and freezing metal between said surface and the inner surface of said opening near the line of contact between said surfaces to seal the closure of said opening.

6. In a method of handling molten aluminum metal wherein a body of molten metal is provided in a holding receptacle and molten metal is passed therefrom through a cylindrical opening in said receptacle, the improvement for stopping flow of molten metal through said opening comprising the steps of closing said opening with a resilient refractory fiber conical surface capable of withstanding temperatures ranging from 1200 F. to 1800 F. and retaining resilience at such temperatures and freezing metal between said conical surface and the inner surface of said opening to provide a seal for stoppage of molten metal flow.

7. An apparatus for releasing and stopping the flow of molten metal from a molten metal holding receptacle comprising a tapping block provided with an orifice for passage of said molten metal, a plug which partially fits within the said orifice wherein a line of contact may be made between the outer peripheral surface of said plug and the inner periphery of said orifice, and a resilient refractory fiber material covering said plug in the area of contact between the said plug and said orifice, said resilient refractory fiber material being characterzed by resistance to attack by molten aluminum and the ability to retain its resilience at temperatures ranging from 1200 F. to 1800 F.

8. The apparatus of claim 7 wherein said resilient refractory fiber material is an aluminum-silicate material.

9. The apparatus of claim 7 wherein said resilient refractory fiber material completely covers the portion of said plug within said orifice, said plug being substantially conical.

10. An apparatus for releasing and stopping the flow of molten metal from a molten metal holding receptacle comprising a tapping block provided with an orifice having a cylindrical bore, a conical cast iron plug which partially fits within said orifice wherein a line of contact may be made between the outer peripheral surface of said plug and the inner periphery of said orifice, and an aluminumsilicate fiber material covering said conical plug in the area of contact between said plug and said orifice.

11. An apparatus for releasing and stopping the flow of molten metal from a molten metal holding receptacle comprising a refractory tapping block provided with an orifice for passage of said molten metal, a plug which partially fits within the said orifice wherein a line of contact may be made between the outer peripheral surface of said plug and the inner periphery of said orifice, a resilient refractory fiber material covering said plug in the area of contact between said plug and said orifice, said resilient refractory fiber material being characterized by resistance to attack by molten aluminum and the abil- &124 354 ity to retain its resilience at temperatures ranging from 1200 F. to 1800 F., the included angle between the surface of said plug and the inner surface of said orifice being less than 4S.

References Cited in the file of this patent UNITED STATES PATENTS 500,386 Hartman June 27, 1893 8 Freeman Sept. 3, Booth Apr. 26, Sander Dec. 10, Dobscha Aug. 25, Whittaker Dec. 14, Slck Oct. 28, Kuharski Oct. 25, Staufer Apr. 10,

Burkett Apr. 10, 

10. AN APPARATUS FOR RELEASING AND STOPPING THE FLOW OF MOLTEN METAL FROM A MOLTEN METAL HOLDING RECEPTACVLE COMPRISING A TAPPING BLOCK PROVIDED WITH AN ORIFICE HAVING A CYLINDRICAL BORE, A CONICAL CAST IRON PLUG WHICH PARTIALLY FITS WITHIN SAID ORIFICE WHEREIN A LINE OF CONTACT MAY BE MADE BETWEEN THE OUTER PERIPHERAL SURFACE OF SAID PLUG AND THE INNER PERIPHERY OF SAID ORIFICE, AND AN ALUMINUMSILICATE FIBER MATERIAL COVERING SAID CONICAL PLUG IN THE AREA OF CONTACT BETWEEN SAID PLUG AND SAID ORIFICE. 